Motion control or movement limitation is important in kinetic assemblies, especially related to precise movement control such as allowing movement in one axis and significantly restricting movement in other axes. In one application, for a scroll compressor as an example, a positive displacement scroll is utilized via having a static Archimedes-type scroll channel and a mating dynamic Archimedes-type scroll channel, wherein the dynamic scroll channel moves in an eccentric manner in relation to the static scroll channel, thus causing a peristaltic-type fluid pumping action between the dynamic and static scroll channels. Although this type of compressor is well known in its basic form, there are desired modifications to the dynamic retention structure as between the dynamic and static scroll channels for more precise control and movement between the dynamic and static scroll channels wherein of necessity the dynamic scroll channel is eccentrically driven, typically by a motor with a rotationally offset output shaft that is operational to drive the dynamic scroll channel in an eccentric rotational motion.
Of course several problem arise with this type of drive train system. The first problem is the drive train system being off balance as a result of rotating a mass eccentrically, which requires a counteracting offset mass placed somewhere in the drive train system. The second problem is that there are multiple limits on the eccentric offset, wherein the hard structural eccentric limits on the structural dynamic interface between the dynamic and static scroll channels have a conflict with the hard structural offset of the drive motor output shaft eccentric offset. Thus these two eccentric offsets, being the dynamic structure between the dynamic and static scroll channels and the drive motor eccentric offset output shaft, effectively place two limits on eccentric rotational movement of the drive train system, wherein the conflict comes from essentially differential manufacturing tolerances, that within thousandths of an inch forces different eccentric limits, thus adding to drive train force and stress, resulting in higher vibration and loss of efficiency, plus potential accelerated component part wear.
One solution is to remove one of the eccentric limits, which of course would have to be in the structural dynamic interface between the dynamic and static scroll channels, as the drive motor eccentric output shaft offset is absolutely required to make the scroll compressor functional, i.e. driving the dynamic scroll channel in the required eccentric rotational motion. The issue with this solution is that typically an Oldham-type coupling is used at the structural dynamic interface between the dynamic and static scroll channels, which in a positive sense creates no eccentric offset limits, however, is less controlled (higher free movement tolerances) and requires lubrication and maintenance that all results in a less precise movement control between the dynamic and static scroll channels, which in turn reduces compressor efficiency. Another solution is to add a structural buffer in the drive train to cushion the conflict between the multiple limits on the eccentric offset, wherein the hard structural eccentric limits on the structural dynamic interface between the dynamic and static scroll channels have a conflict with the hard structural offset of the drive motor output shaft eccentric offset. This solution would maintain the high level of desirable control between the dynamic and static scroll channels while at the same time reducing wear, vibration, and inefficiency.
Looking at the prior art in this area, U.S. Pat. No. 6,736,622 to Bush, et al. discloses a scroll compressor comprising: a first scroll member having a base and a generally spiral wrap extending from said base; a second scroll member having a base and a generally spiral wrap extending from its base, a drive shaft having an eccentric pin for causing said second scroll member to orbit relative to said first scroll member. In Bush, the wraps of the first and second scroll members are interfitting to define compression chambers which are reduced in volume as the second scroll member orbits relative to said first scroll member. The wraps of the first and second scroll members are each formed from an origin on the first and second scroll members respectively, see Bush's FIGS. 2 and 3. Plus, each of the first and second scroll members have drive centers, with the drive center of the first scroll member being defined as a central axis of the drive shaft and the drive center of the second scroll member being defined as a center axis of the eccentric pin.
Further, in Bush, the origin of each of the first and second scroll members is offset in a similar direction from the drive centers of the first and second scroll members, with the offset being selected to reduce torque fluctuation and torque reversal during orbital motion of the second scroll member, see Bush's FIG. 4. Thus, Bush's wraps of the first and second scroll members are hybrid wraps, with variable thickness along a circumferential length of the wrap. Thus, in Bush, an origin point exists at the theoretical start of the scroll, which has typically been the offset motor drive center line also. In Bush there is an added offset to the existing offset center line of the drive scroll to specifically reduce drive torque amplitudes that come from pressure differences within the scrolls. Thus, Bush recognizes the problem of vibration, wear, and inefficiency from the eccentric movement in the scroll compressor and basically has a static double offset from the scroll centerline to the motor drive output shaft offset centerline to help alleviate torque reversals from the eccentric rotational movement.
Continuing in the prior art, U.S. Pat. No. 6,712,589 to Mori, et al. discloses a scroll compressor comprising: a compressor housing having an inlet port and an outlet port, and a drive scroll rotatably disposed within the compressor housing and having a rotational axis. In Mori, a driven scroll is rotatably disposed within the compressor housing and has a rotational axis, wherein the driven scroll rotational axis is offset to the drive scroll rotational axis and at least one compression chamber is defined between the drive scroll and the driven scroll. Further, in Mori a first bearing rotatably supports the drive scroll in a cantilever manner, a second bearing rotatably supports the driven scroll in a cantilever manner, and a means for permitting the driven scroll to move along the axial direction is provided.
Also, Mori has a means for biasing the driven scroll towards the drive scroll in an axial manner, wherein the biasing means comprises a discharge chamber defined within the compressor housing, the discharge chamber communicating with the outlet port and being disposed adjacent to the driven scroll, wherein refrigerant drawn into the at least one compression chamber via the inlet port and compressed within the at least one compression chamber is discharged into the discharge chamber, and the compressed refrigerant applies a force against the driven scroll that urges the driven scroll toward the drive scroll. In Mori, an Oldham coupling is used as in the prior art as being an offset drive coupling that utilizes an engaging slot disc with opposing slots typically perpendicular to one another, wherein the slots have a slidable engagement with one another. The novelty in Mori is in the axial compression control as between the scrolls.
Next in the prior art, U.S. Pat. No. 9,022,758 to Roof, et al. discloses a scroll compressor, comprising: a housing defining an internal cavity; a separator within the internal cavity of the housing separating a high pressure chamber from a low pressure chamber, the separator including a port fluidly communicating with the high pressure chamber; a fixed scroll body positioned within the low pressure chamber including a base, a scroll rib axially extending from a first side of the base, and an axially extending circular hub on a second opposite side of the base. In Roof, the circular hub defines a compression outlet extending through the circular hub and fluidly communicating with the high pressure chamber through the port. Further, a floating seal arrangement is interposed between the fixed scroll body and the separator, the floating seal arrangement sealing the compression outlet to the port and being axially moveable relative to the circular hub.
In Roof, the floating seal arrangement includes: a floating seal; a first seal interface between the separator and the floating seal; a second seal interface between the floating seal and the circular hub, the second seal interface including a first seal member interposed between the circular hub and the floating seal; and a seal retaining ring limiting axial movement of the first seal member relative to the circular hub and extending away from the base of the fixed scroll body. Also in Roof, the first seal member is a spring energized seal including a resilient seal jacket and a seal spring positioned within the resilient seal jacket. The resilient seal jacket is generally U-shaped in cross-section defining opposed seal surfaces, with the seal spring positioned between the opposed seal surfaces. Roof has the opposed seal surfaces being a radially outer leg portion and a radially inner leg portion facing generally radially away from one another, wherein the seal retaining ring has an outer diameter that is greater than an inner diameter of the radially inner leg portion when the retaining ring and the first seal member are attached to the fixed scroll body. Thus, in Roof the outer diameter of the seal retaining ring is greater than an inner diameter of the seal spring, wherein Roof has a limited axial motion of the seal with a seal retaining ring.
Next in the prior art, U.S. Pat. No. 8,007,260 to Yanagisawa discloses a scroll fluid machine that has a stationary scroll having a stationary scroll lap fixed to a scroll casing and an orbiting scroll having an orbiting scroll lap that orbits relative to the stationary scroll lap. In Yanagisawa, the stationary and orbiting scrolls are connected via a coupling mechanism other than an Oldham coupling or pin crank type mechanism having sliding parts. The coupling mechanism includes plate springs that connect the stationary scroll to the orbiting scroll. The orbiting scroll lap in Yanagisawa engages with the stationary scroll lap to form a closed compression chamber. This is essentially an offset drive coupling that has different structure from the Oldham coupling, via using plate spring members to eliminate the slidable engagement of slots that the Oldham coupling has, thus also eliminating lubrication from metal to metal rubbing. However, Yanagisawa does not address problems of spring fatigue and centrifugal forces acting upon the springs from rotation.
Continuing in the prior art, U.S. Pat. No. 6,379,134 to Iizuka discloses a scroll compressor comprising paired fixed and movable scrolls, the fixed scroll of each pair having an end plate provided with a scroll body projecting from the end plate and the movable scroll of each pair having an end plate provided with a scroll body projecting from the end plate. In Iizuka, the movable scroll meshes with the fixed scroll to form a plurality of operation chambers between them and revolves relative to the fixed scroll to compress gas in the operation chambers. Two pairs of fixed and movable scrolls are disposed with back faces of the end plates of the fixed scrolls opposite each other. The movable scrolls in Iizuka are integrally connected with each other, a main shaft for revolving the movable scrolls passes through the two pairs of fixed and movable scrolls to operatively engage the movable scrolls, and an outlet chamber is disposed between the end plates of the fixed scrolls. Thus, Iizuka attempts to axially balance compressor pressures with two opposing pairs of static and dynamic scrolls.
What is needed is a rotational eccentric structural buffer in the scroll compressor drive train to cushion the rotational eccentric conflict between the multiple eccentric movement limits on the eccentric offset, wherein the hard structural eccentric limits on the structural dynamic interface between the dynamic and static scroll channels have a conflict with the hard structural offset of the drive motor output shaft eccentric offset. This solution would maintain the high level of desirable movement control between the dynamic and static scroll channels (via not using an Oldham coupling) while at the same time reducing wear, vibration, and inefficiency of the scroll compressor drive train as a whole. Ideally this solution would be permanent in nature and not require any additional maintenance.